In recent years, analysis agents have provided a service to analyze data obtained from a client via, for example, a Virtual Private Network (VPN), and to provide the client with results obtained from the analyzing. When the client requests, for each user, an analysis result on data obtained from each individual user, data to be analyzed is associated with personal information to identify the user. Accordingly, in many cases, in order to prevent personal information from leaking from data given to the analysis agent, clients perform a process of replacing the personal information with, for example, pseudonym, which can uniquely specify an individual, and then give the processed data to the analysis agent. The analysis agent analyzes the data obtained from the client and associates an analysis result for each user with pseudonym. In addition, the analysis agent associates the obtained analysis result with pseudonym and then provides the client with this result. The client replaces the pseudonym associated with the analysis result obtained from the analysis agent with personal information of a user. Meanwhile, the user requests an analysis result obtained for this user from the client. Accordingly, the client provides the user who has requested an analysis result with the analysis result associated with this user.
As a related art, a single sign-on system is known that includes: a user terminal; a service server; and an authentication server for performing authentication when the user terminal logs in the service server. When authentication is successful, the authentication server connects a user ID with an identifier unique to the service server which has made a request for authentication, and generates an encrypted new ID, and transmits it to the user terminal. When a service use is requested together with a new ID, the service server obtains user information from the authentication server by using the new ID. A system is also known wherein, when a line ID corresponding to an address specified by inquiring with a network management device is identical with a registered line ID specified based on a link ID, encrypted information for presentation information corresponding to the link ID and the registered link ID is transmitted to a user terminal.